Presently, known state-of-the-art dispenser/filler utilize a cylinder and piston arrangement with an inlet valve for introducing material and an outlet valve for expelling the material. While this arrangement has proven satisfactory in the past as it provides a generally reliable system with a high degree of volume control, it presents several distinct drawbacks. For example, the cylinder and piston apparatus contains crevices and stagnant flow packets that present prime areas in which bacteria can grow and, accordingly, present a sanitary risk and, worse, a health risk. The above apparatus also depends on various sealing techniques which further pose sanitary, and therefore health risks as the seals utilized frequently wear out and leak, again providing perfect breeding places for potentially harmful bacteria. As can be easily understood, the uncontrolled growth of bacteria germs can be especially dangerous when processing products requiring a high degree of cleanliness.
While it is generally the practice to routinely clean the presently known fillers on a daily basis, more extensive and thorough cleaning is periodically required. It is not uncommon for this procedure to require in excess of 30 hours to complete. Obviously, the resulting down time of the apparatus combined with the costs of labor involved in performing the service can lead to increased cost of the final product.
Ideally, a filler should operate such that the material first introduced is the material first expelled (the FI-FO principle; first in, first out) to avoid the possibility that stagnant pockets of product may occur which result in sanitary problems. It is known that a peristaltic pumping device (either roller type or cam type) can provide such results. However, presently know peristaltic pumping devices are not satisfactory from the standpoint of accuracy of delivery, especially when volumes other than defined by the spaces in the tube along the path of a squeeze roller is required. Also since bare plastic tubing of a relatively soft grade is frequently utilized, both temperature and pressure variations, especially at the intake, will vary the quantity delivered. Even if a fabric covering (generally of a helical woven material) is provided as a sheath for the plastic tubing, variations in either temperature or pressure, or both, are likely to occur. Still further, most generally well known peristaltic action pumps utilize a roller assembly of some type which is revolved so as to squeeze a flexible tube against a wall surface. This is less than satisfactory, as the rolling/squeezing action of the roller assembly is directed against one surface of the tubing containing the material being pumped. Accordingly, certain areas of the tubing are submitted to added stresses and strains.
A further problem incurred by presently know peristaltic pumps, is the flow condition encountered at the delivery point which is generally a nozzle of some kind. Depending upon the viscosity of the material, the air entrained in the material, and the distance between the pumping device and the nozzle, varying degrees of nozzle "drool" may result. That is, some of the product delivered from the tubing may not actually wind up as fill in the intended receptacle but, remain in the form of strands on the end of the tubing. These strands can easily become contaminated before the next discharge of material thereby contaminating that fill and, potentially, subsequent fills.
Still further, the above condition can present problems with sanitation in the event that the containers being filled must be closed by heat sealing a foil or membrane ave their openings. The likelihood of a deflective seal caused by the "drool" and subsequent product spoilage is quite high if the sealing surface is contaminated by product.